This invention relates generally to strobe lamp systems and particularly to an improved switching arrangement for a strobe lamp intensity control system.
U.S. Pat. No. 3,792,309 issued Feb. 12, 1974 and assigned to Multi Electric Manufacturing, Inc. discloses an intensity control system for a strobe lamp of the type commonly used in airplane landing approach lighting systems. The patented system includes an igniter controlled strobe lamp, the intensity of which is selectable by a local or remotely controlled intensity switch for controlling the discharge of various energy storing capacitors through the strobe lamp. In particular, the intensity switch may be controlled by aircraft operating personnel, e.g. a pilot, via a wireless communications link. The intensity of the lamp is directly related to the total available energy therethrough which is a direct function of the number and capacitance of the capacitors permitted to discharge through the lamp. A variable intensity is required to accommodate changes in atmospheric visibility at the landing site and the Federal Aviation Authority (FAA) requires an ability to switch intensity of the strobe lamps without a significant time interruption. The patented system uses a combination of make/break relay contacts to control the charging and discharging of the capacitors. The system of the patent has been in use for many years with highly satisfactory results.
The present invention improves upon the prior art patented circuit by increasing the reliability of the relay switches, particularly the relay switch contacts, and extending the life of the capacitors. This is accomplished by incorporating diodes across the relay contacts that complete the charge paths for the capacitors. The diodes enable all of the storage capacitors to be continually charging and thereby to maintain their charge levels when the system is on, irrespective of the position of the intensity switch, to reduce transient currents during switching. Another aspect of the invention provides synchronization for further transient current reduction.